Implantable medical devices may perform various functions in order to deliver modes of therapy to a patient. For example, cardiac stimulation devices like pacemakers and defibrillators may sense electrical physiologic signals in some modes of therapy in addition to providing electrical pacing signals to one or more chambers of the heart. Some modes of therapy that sense a physiologic signal then use that signal when determining how to control the pacing signal.
Patients that have an implantable medical device may be exposed to magnetic disturbances like those caused by MRI scans or other medical procedures. These magnetic disturbances may result in the device sensing signals that are not actually physiologic but are artificially created by the magnetic disturbances. If the device is allowed to control the pacing signal based on the sensed artificial signal, then the pacing signal may be inappropriate or even harmful for the patient. Therefore, it is commonplace to utilize an exposure mode of therapy during such disturbances where the exposure mode deactivates sensing or otherwise ignores the sensed signal and paces asynchronously in a pre-defined pacing configuration with a pre-defined pacing rate. This may not be an optimal exposure mode of therapy, especially for certain patients having particular device types such as those with pacing ability but being primarily for defibrillation purposes. Likewise, the pre-defined pacing rate may not be an optimal rate of pacing for patients with other pacing needs.